The contents of this paper record the results of a detailed examination of certain extensive areas of dolomitization in the Carboniferous Limestone of the Midlands. During the period 1912 to 1914 the faunal succession in the Carboniferous Limestone bordering the Leicestershire Coalfield chiefly claimed my attention, but many problems associated with dolomitization arose in connexion with that work and have been discussed in a previous paper. Being thus introduced to a study of metasomatism which yielded interesting results in Leicestershire, I turned my attention to the larger Carboniferous Limestone outcrop in Central Derbyshire, where a considerable thickness of dolomitized beds awaited description. The question as to whether the dolomitization in Derbyshire affected material on similar horizons or exhibited other features analogous to those of the dolomitization of the Leicestershire outcrops afforded considerable scope for investigation. Additional incentive to this particular study lay in the fact that dolomitization in the Carboniferous Limestone of this country had not been treated as a principal theme, but had been briefly described in notes occurring in papers by various authors, whose main object was the elucidation of other problems such as faunal succession.

The Lettereeneen fault, a newly recognized structure, brings the Mweelrea and Maumtrasna Groups of the Partry Series (Caradocian-Llandeilian age) into contact. The stratigraphy of the Mweelrea Group, of red bed facies, is followed from the presence of welded tuff horizons; no such markers exist in the Maumtrasna Group which lies unconformably upon the former.

Sedimentary structures of shallow water origin occur in each group. Three types of conglomerate recognized in the area are examined. The immature feldspathic sandstones increase in arkosity upwards.

A proluvial or proluvio-marine environment of deposition is suggested, with debris derived from an eastward extension of the metamorphosed Dalradian rocks of the Connemara Cordillera and foothills of sedimentary and volcanic rocks.

In France deposits of the same kind, such as those at Menchecourt, are familiar enough. To complete our merely illustrative list of examples, I would quote the vast deposits found in the offing of the Thames, and right away to the Dutch coast. Dr. Bree says that the bones occur in such quantities on the sea-bottom off Dunkirk that the sailors call it the Burying Ground (Leith Adams's Mem. on Elephas primigenius, p. 73).

My attention having been directed, during the construction of the Main Outfall Sewer at Birkdale, to the Post-Glacial deposits underlying the great plain between Waterloo and Crossens, and having, through the execution of numerous other works in the district, peculiar advantages for prosecuting investigations in Post-Glacial Geology, I am induced to lay before your readers several interesting facts, and also, as I venture to think, some important deductions therefrom.

Between the Cruachan Granite complex and the Glen Strae fault, to the south-east, and the Pass of Brander fault, to the south-west, there is a strip of Dalradian rocks (Fig. 1). These all lie within 1 in. Sheet 45 (Scot.) of the Geological Survey and are described in the Oban and Dalmally Memoir (Hill, 1908, pp. 19–28; Kynaston, 1908, pp. 38–40). Bailey has later distinguished the three great structural divisions into which he has divided the South-West Highlands. These are, in ascending structural succession: the Ballapel Foundation, represented south-east of the granite by Eilde Flags, Glencoe Quartzite, Leven Schists, and Ballachulish Limestone, and south-west of the same by Leven Schists; the Iltay Nappe, represented in both these positions by Islay Quartzite and Easdale Slates; and the Loch Awe Nappe, represented south of the granite by Ardrishaig Phyllites (Bailey, 1922).

Diamond Region.—The diamond-bearing region in South Africa, as at present known, is chiefly within the valley ofthe Vaal River and some of its tributaries (as the Modder and the Vet); but it is known also to extend down the Orange (Gariep) Valley for a few miles after the junction of its two great branches, the Ky Gariep (Vaal) and the Nu Gariep (CradockRiver). Bloemhof on the Vaal, two hours (12 miles) south-west of Potscherfstroom (Trans-vaal), is the reported locality ofthe most northern diamond-find. Below, for a distance of 370 miles, the plain has yielded diamonds, at several places, on both sides of the river, at Hebron, Klipdrift (near Pniel), Zitzikammsi, Vogelstmis Pan, Sitlacomie's Village, Sikoneli's Village, Nicholson's Farm, Kalk Farm (near Litkatlong), etc.; and on the south side of tie Orange River, they have been found some miles north-west of Hopetown, at Probeerfontein, Roodekop, David's Pan, etc. Diamondsare also said to have been found a few miles east of Fauresmith, on a branch of the Modder, about 100 miles south by east of Litkatlong; also a few miles south of Winburg (also in the Orange River Free State), in the upper drainage of the Vet River, about 80 miles from the Vaal.

In the case of a vertical cliff, Mr. Fisher has shown that the uneroded surface of rock underneath a talus is in the form of a semi-parabola.1 The object of this note is to show that the form is parabolic, even if the cliff be not initially vertical, assuming, with Mr. Fisher, (1) that the cliff-face is weathered uniformly at all points, and (2) that the disintegrated material is spread evenly over the surface of the talus, so as to maintain it always at the same slope. The proposition may be proved analytically, as in Mr. Fisher's paper, or geometrically as follows.

A new ammonite assemblage from the Ampthill Clay is recorded. Its correlation with the Trigonia clavellata beds of Dorset indicates that these condensed beds are represented by two distinct horizons in the Ampthill Clay—the Boxworth Rock below and the Knapwell Ditch horizon above.